The large investments in the microelectronics industry converted integrated circuits laboratories into machine shops where miniature electromechanical systems are designed and built. Electromechanical as well as electro-optical systems have been miniaturized and used in many different applications. In the same fashion, miniaturization is presently applied in the field of microfluidics. Microfluidics technology provides the advantage of being able to perform chemical and biochemical reactions and/or separations with high throughput low volumes. Microfluidic systems employ microchannels in which chemical and biochemical materials are transported, mixed, separated and detected. The object is to take advantage of development in the silicon micromachining industry to develop laboratories on chips where fluids are manipulated, transported and tested. Electric and optical fields form the backbone of most of the methods used today in the transport and characterization of the fluids in channels.
Ultrasonic devices using piezoelectric materials have been successfully used for measurements of flow, physical properties and pressure of fluids and gases in many applications. Most of these devices are bulky, and they cannot be easily integrated to microfluidic systems for several reasons. With a few exceptions, piezoelectric materials are not compatible with other processing steps required for the fluidic chips. In addition, piezoelectric transducers for bulk wave excitation cannot be scaled down easily so as to fit in microfluidic channels without degrading their performance.